Figure 3. Effects of leaf water status and ABA signal on the chilling tolerance of JY-3 leaves and JC-4 leaves.

The maximum quantum yield of PSII (Fv/Fm, a,c,e,g,i) and the amount of PSI (b,d,f,h,j) in leaves of JY-3 and JC-4 seedings that exposed to whole plant chilling-light treatment (a,b,g,h), shoot-special chilling-light treatment (c,d,i,j) and whole plant chilling-light treatment with attached leaves floated on cool water (e,f) under 150 μmol m⁻² s⁻¹ light. Before chilling-light treatment, the leaves were sprayed by 100 μM (+ABA) or 1000 μM (+high ABA) ABA solution (with 0.02% Tween 20) or 0.02% Tween 20 solution (-ABA). In the whole plant chilling treatment, plants were exposed to 6 °C. In the shoot-special chilling treatment, the shoots were exposed to 6 °C and the roots were exposed to 25  °C. Values represent the means ± SE, and each data point is the average of 10 independent plants. Different letters indicate significant differences between different cucumber varieties at P < 0.05.